Department of Plant Breeding, Institute of Crop Science and Resource Conservation, University of Bonn, Germany.
Department of Entomology and Nematology, UC, Davis, USA.
J Plant Physiol. 2021 Jun;261:153414. doi: 10.1016/j.jplph.2021.153414. Epub 2021 Apr 10.
Proline accumulation is one of the most common adaptive responses of higher plants against abiotic stresses like drought. It plays multiple roles in osmotic adjustment, cell homeostasis and stress recovery. Genetic regulation of proline accumulation under drought is complex, and transcriptional cascades modulating proline is poorly understood. Here, we employed quadruple mutant (abf1 abf2 abf3 abf4) to dissect the role of ABA-responsive elements (ABREs) binding transcription factors (ABFs) in modulating proline accumulation across varying stress scenarios. ABREs are present across the promoter of the P5CS1 gene, whose upregulation is considered a hallmark for drought inducible proline accumulation. Upon ABA treatment, P5CS1 mRNA expression and proline content in the shoot were significantly higher in Col-0 compared to the quadruple mutant. Similar results were found at 2 h and 3 h after acute dehydration. We quantified proline at different time points after drought stress treatment. The proline content was higher in wild type (Col-0) than the quadruple mutant at the early stage of drought. Notably, the proline accumulation in wild type increased at a slower rate than the quadruple mutant 7 d after drought stress. Besides, the quadruple mutant displayed significant oxidative damage, low tissue turgidity and higher membrane damage under terminal drought stress. Both terminal drought stress and long-term constant water stress revealed substantial differences in growth rate between wild type and quadruple mutant. The study provides evidence that ABFs are involved in drought stress response, such as proline biosynthesis in Arabidopsis.
脯氨酸积累是高等植物应对干旱等非生物胁迫的最常见的适应性反应之一。它在渗透调节、细胞内稳态和胁迫恢复中发挥着多种作用。在干旱条件下，脯氨酸积累的遗传调控非常复杂，而调节脯氨酸的转录级联反应还了解甚少。在这里，我们利用四重突变体（abf1 abf2 abf3 abf4）来解析 ABA 响应元件（ABREs）结合转录因子（ABFs）在不同胁迫情况下调节脯氨酸积累中的作用。ABREs 存在于 P5CS1 基因的启动子中，该基因的上调被认为是干旱诱导脯氨酸积累的标志。在 ABA 处理后，Col-0 中 P5CS1 mRNA 的表达和脯氨酸含量明显高于四重突变体。在急性脱水后 2 小时和 3 小时也发现了类似的结果。我们在干旱胁迫处理后不同时间点定量了脯氨酸。在干旱早期，野生型（Col-0）中的脯氨酸含量高于四重突变体。值得注意的是，在干旱胁迫 7 天后，野生型中的脯氨酸积累增加速度比四重突变体慢。此外，在终末干旱胁迫下，四重突变体表现出明显的氧化损伤、组织膨压低和膜损伤增加。在终末干旱胁迫和长期持续水分胁迫下，野生型和四重突变体之间的生长速度都有显著差异。该研究提供了证据表明 ABFs 参与了拟南芥的干旱胁迫反应，如脯氨酸的生物合成。
